Imaging apparatuses such as a camera and a video camera have been desired to capture a less-blur image of various subjects distributed in a wide range of a distance from a photographic optical system. In other words, it has been desired to extend a depth of field of the photographic optical system. Although adjustment of an aperture to increase an F value allows the extension of the depth of field, the increase in the F value causes lack of light of an optical image of the subject to be received on the light receiving surface. Therefore, it is necessary to slow down a shutter speed or to increase an ISO sensitivity of a film or an area sensor. However, slowing down the shutter speed makes it difficult to capture a moving subject. Also, there has been a problem that the increase in the ISO sensitivity causes an increase in noise generated in a captured image.
As such, there has been proposed a method of debluring, by means of a phase mask, by regularly distributing light beams such that a response of an optical transfer function of the photographic optical system becomes substantially insensitive to a wide range of a subject distance and carrying out deconvolution processing on a captured distributed image (see Patent Document 1 and Patent Document 2). According to the invention described in Patent Document 1, blur occurs in the image of a subject positioned at the subject distance within the above range. However, since the light beams are regularly distributed, restoration processing allows a reduction in blur of the subject positioned at various subject distances and the depth of field may be extended.
However, according to the inventions described in Patent Document 1 and Patent Document 2, the response of the optical transfer function of the photographic optical system using the phase mask is low overall. Therefore, there has been a problem that the noise increases when the restoration processing is carried out in order to satisfactory reduce blur.